Field of the Invention
The present invention relates to an optical system and an imaging apparatus including the same. The present invention is suitable for imaging apparatuses, such as a digital still camera, a video camera, a security camera, and a broadcast camera, including imaging devices; and imaging apparatuses such as a silver-halide camera.
Description of the Related Art
Known focusing methods widely employed in imaging lens systems include an inner focus method and a rear focus method in each of which a lens provided at a position on the image side with respect to a lens provided at the extreme end on the object side is moved for focusing.
Herein, a focusing technique in which a lens provided on the image side with respect to an aperture stop is moved for focusing is referred to as the “rear focus method”, and a focusing technique in which a lens provided on the object side with respect to the aperture stop is moved for focusing is referred to as the “inner focus method”.
In an imaging lens system employing the inner focus method or the rear focus method, since a relatively small lens is moved for focusing, quick focusing action can be realized.
On the other hand, a macro lens system is known as an imaging lens system intended mainly for short-range imaging with a substantially 1× magnification. An optical system forming the macro lens system is desired to exhibit high optical performance in short-range imaging.
An optical system disclosed by Japanese Patent Application Laid-Open No. 2012-159613 is capable of short-range imaging and employs the rear focus method.
However, in the optical system disclosed by Japanese Patent Application Laid-Open No. 2012-159613, since the refractive power of the focus lens unit is excessively strong, the degree of aberration tends to vary with focusing. Moreover, since the focusing lens unit has the strong negative refractive power, the sizes of optical members provided on the image side with respect to the focusing lens unit tend to increase.